Support for non-RTX fallback

[Calinou]

OS: Fedora 34 (running the Windows build with wine-staging 7.2)
GPU: NVIDIA GeForce GTX 1080

Inspired by sultim-t/prboom-plus-rt#12 (comment), I tried to use the same RaytracedGL1.dll with Serious Sam Ray Traced 1.5 by placing it in the Bin/ folder. Unfortunately, I'm still getting a black screen on launch after the initial "Serious Sam will start for the first time" dialog. I can hear sounds when hovering menu items, and it's even possible to start a game by pressing Enter several times in a row (without moving the mouse).

Just to exclude something like godotengine/godot#18320 happening (which shouldn't affect Vulkan applications anyway), I tried to disable the MSAA override I set at the driver level to no avail.

Is there anything else I could try to make the non-RTX fallback work? I know this will be slow, but from my testing with Quake 2 RTX and prboom-plus-rt, it should be possible to get playable framerates on this GPU by playing at 640×480 and low RT settings.

Edit: Tested this on Windows 10 as well, the executable exists as soon as I acknowledge the first start dialog (no black screen).

[kodatarule]

For me on my RTX 3070, it runs just fine sometimes I can even play for quite long, but soon it just exits, wine log doesn't contain anything useful and the results are the same with Proton.